missing memory

Ordered a i7 27" w/ 8GB memory, all paperwork showed this as well as the box in came in. Checked a few weeks later and it was 2 X 2, NOT 2 X 4. Someone else here had rec'd 12GB instead of 8. Anyone else had this problem?? All is OK because they will get the memory installed ASAP, so that nice. Wonder how this happened??
Terry D